There are a number of cafés in each arrondissement which offer Freewireless for drinking customers for 20 minutes at a time. Here are a couple in the first:
wireless hotspots
Tabac du Châtelet
8, rue Saint Denis
Métro: Châtelet
wireless hotspots
Chez Flottes
2, rue Cambon
Métro: Concorde
wireless hotspots
Of course many hotels also offer wireless connectivity, but usually for a fee.
wireless hotspots
A complete listing is available from the company which provides the service: